Mercury (Hg) exposure remains a major public health concern due to its widespread distribution in the environment. Organic mercurials, such as MeHg, have been extensively investigated especially because of their congenital effects. In this context, studies on the molecular mechanism of MeHg-induced neurotoxicity are pivotal to the understanding of its toxic effects and the development of preventive measures. Post-translational modifications (PTMs) of proteins, such as phosphorylation, ubiquitination, and acetylation are essential for the proper function of proteins and play important roles in the regulation of cellular homeostasis. The rapid and transient nature of many PTMs allows efficient signal transduction in response to stress. This review summarizes the current knowledge of PTMs in MeHg-induced neurotoxicity, including the most commonly PTMs, as well as PTMs induced by oxidative stress and PTMs of antioxidant proteins. Though PTMs represent an important molecular mechanism for maintaining cellular homeostasis and are involved in the neurotoxic effects of MeHg, we are far from understanding the complete picture on their role, and further research is warranted to increase our knowledge of PTMs in MeHg-induced neurotoxicity. 相似文献
Lipase (EC 3.1.1.3) from Candida rugosa was covalently immobilised on to cellulose, cellulose derivatives (cellulose acetate and cellulose phthalate) and cellulose composite membranes using activating agents such as sodium periodate or carbodiimide. Other non-cellulosic polymeric membranes (nylon, polyurethane, chitosan and hydroxyethyl methacrylate-co-methyl methacrylate) were also prepared and used for lipase immobilisation. The results obtained showed that the expressed activities are of the same order of magnitude for similar enzyme loadings when compared with those obtained from literature. 相似文献
The variation of amino acid substitution rates in proteins depends on several variables. Among these, the protein's expression level, functional category, essentiality, or metabolic costs of its amino acid residues may play an important role. However, the relative importance of each variable has not yet been evaluated in comparative analyses. To this aim, we made regression analyses combining data available on these variables and on evolutionary rates, in two well-documented model bacteria, Escherichia coli and Bacillus subtilis. In both bacteria, the level of expression of the protein in the cell was by far the most important driving force constraining the amino acids substitution rate. Subsequent inclusion in the analysis of the other variables added little further information. Furthermore, when the rates of synonymous substitutions were included in the analysis of the E. coli data, only the variable expression levels remained statistically significant. The rate of nonsynonymous substitution was shown to correlate with expression levels independently of the rate of synonymous substitution. These results suggest an important direct influence of expression levels, or at least codon usage bias for translation optimization, on the rates of nonsynonymous substitutions in bacteria. They also indicate that when a control for this variable is included, essentiality plays no significant role in the rate of protein evolution in bacteria, as is the case in eukaryotes. 相似文献
RCK (regulating conductance of K+) domains are common regulatory domains that control the activity of eukaryotic and prokaryotic K+ channels and transporters. In bacteria these domains play roles in osmoregulation, regulation of turgor and membrane potential and in pH homeostasis. Whole-genome sequencing unveiled RCK gene redundancy, however the biological role of this redundancy is not well understood. In Bacillus subtilis, there are two closely related RCK domain proteins (KtrA and KtrC) that regulate the activity of the Ktr cation channels. KtrA has been well characterized but little is known about KtrC. We have characterized the structural and biochemical proprieties of KtrC and conclude that KtrC binds ATP and ADP, just like KtrA. However, in solution KtrC exist in a dynamic equilibrium between octamers and non-octameric species that is dependent on the bound ligand, with ATP destabilizing the octameric ring relative to ADP. Accordingly, KtrC-ADP crystal structures reveal closed octameric rings similar to those in KtrA, while KtrC-ATP adopts an open assembly with RCK domains forming a super-helix. In addition, both KtrC-ATP and -ADP octamers are stabilized by the signaling molecule cyclic-di-AMP, which binds to KtrC with high affinity. In contrast, c-di-AMP binds with 100-fold lower affinity to KtrA. Despite these differences we show with an E. coli complementation assay that KtrC and KtrA are interchangeable and able to form functional transporters with both KtrB and KtrD. The distinctive properties of KtrC, in particular ligand-dependent assembly/disassembly, suggest that this protein has a specific physiological role that is distinct from KtrA. 相似文献
Hydrogen is a clean energy alternative to fossil fuels. Photosynthetic bacteria produce hydrogen from organic compounds by an anaerobic light-dependent electron transfer process. In the present study hydrogen production by three photosynthetic bacterial strains (Rhodopseudomonas sp., Rhodopseudomonas palustris and a non-identified strain), from four different short-chain organic acids (lactate, malate, acetate and butyrate) was investigated. The effect of light intensity on hydrogen production was also studied by supplying two different light intensities, using acetate as the electron donor. Hydrogen production rates and light efficiencies were compared. Rhodopseudomonas sp. produced the highest volume of H2. This strain reached a maximum H2 production rate of 25 ml H2 l(-1) h(-1), under a light intensity of 680 micromol photons m(-2) s(-1), and a maximum light efficiency of 6.2% under a light intensity of 43 micromol photons m(-2) s(-1). Furthermore, a decrease in acetate concentration from 22 to 11 mM resulted in a decrease in the hydrogen evolved from 214 to 27 ml H2 per vessel. 相似文献
Production of 2,3-butanediol (2,3-BD) by Pantoea agglomerans strain BL1 was investigated using soybean hull hydrolysate as substrate in batch reactors. The cultivation media consisted of a mixture of xylose, arabinose, and glucose, obtained from the hemicellulosic fraction of the soybean hull biomass. We evaluated the influence of oxygen supply, pH control, and media supplementation on the growth kinetics of the microorganism and on 2,3-BD production. P. agglomerans BL1 was able to simultaneously metabolize all three monosaccharides present in the broth, with average conversions of 75% after 48 h of cultivation. The influence of aeration conditions employed demonstrated the mixed acid pathway of 2,3-BD formation by enterobacteria. Under fully aerated conditions (2 vvm of air), up to 14.02 g L−1 of 2.3-BD in 12 h of cultivation were produced, corresponding to yields of 0.53 g g−1 and a productivity of 1.17 g L−1 h−1, the best results achieved. These results suggest the production potential of 2,3-BD by P. agglomerans BL1, which has been recently isolated from an environmental consortium. The present work proposes a solution for the usage of the hemicellulosic fraction of agroindustry biomasses, carbohydrates whose utilization are not commonly addressed in bioprocess.
Probiotics and Antimicrobial Proteins - The use of natural products together with standard antimicrobial drugs has recently received more attention as a strategy to combat infectious diseases... 相似文献
Plant Cell, Tissue and Organ Culture (PCTOC) - Somaclonal variation during in vitro culture is often an undesirable phenomenon but may also be a source of genetic variation useful for breeders. The... 相似文献